Lake Distriet: Interlacustrine Area. 401 
Bluffs and Allwvial Plains. There can be almost no other habitat in our 
climate, which imposes such severe conditions upon vegetation as an eroding 
clay blufl. The first vegetation to appear commonly consists of xerophytic 
herbs both annual and perennial. Among these are Melilotus alba, Aster 
laevis, Equisetum hyemale. Soon there develops a xerophytic thicket vege- 
tation and this may be called the shrub stage of the captured cliff and among 
the dominant ‚species are Juniperus communis and virginiana, Salix glauco- 
phylla, Cornus stolonifera, Shepherdia canadensis, Rhus typhina and glabra. 
The succeeding tree stage is dominated by poplars'’). 
The river bluff formation in the Huron River Valley on till bluffs is marked 
by the presence of Carya alba (= Hicoria ovata), C. tomentosa (= H. alba), 
C. microcarpa (= H. odorata), C. porcina (= H. glabra), with which trees are 
associated Ouercus rubra and O. alba. On the sandy bluffs where the hickories 
and red oaks disappear are found Ouercus tinctoria, O. alba and in other places 
©. imbricaria. 
The flood plain of the Huron River Valley is occupied by a forest growth 
which consists of Populus tremuloides and monilifera, as the early pioneers 
followed by Ulmus americana, U. fulva, Fraxinus pubescens, viridis, sambuci- 
folia, Acer dasycarpum?) and rubrum, Platanus, Tilia, Juglans, Ouercus macro- 
carpa and bicolor. Along the tension line nearest the streams Carpinus caro- 
liniana is common and in similar but drier situation Ostrya virginiana is 
found °). 
4. Bog-Formation. 
The sphagnum bog or moors (muskegs of the Minnesota woodsmen) may 
be regarded as glacial ponds, or lakes, in process of conversion to forest, and 
almost every imaginable transition may be found from open lakes with sandy 
beach lines continuous on all sides to solid masses of spruce and tamarack. 
A description of one of these bogs as found in Minnesota follows. The center of the moor 
is ei softer and more yielding than the edges. ee open eg exists 5 covered 
trieularia, Lemna trisulca or nn of Potamogeton, Nuphar a arther fro 
ee center Kalmia glauca and Andromeda Dolifolin with Pos Sigi, we: pul- 
chellus various species of Carex ar Eriophorum, Salix, Vacc ee Sarracenia purpurea. 
Ledum latifolium grows in drier and more peripheral positions. ur ing this association of 
plants are Picea alba or P. nigra, Larix americana and sundry species of ei Alnus incana and 
Betula pumila, B. glandulosa#). 
1) CowLes, HENRYC.: The physiographie Ecology of Chicago and Vicinity. Botanical Gazette 
XXXI: 164—170 
2) Anmerkung des Herausgebers: HARSHBERGER schreibt A. saccharinum gemäß d Ge- 
brauch von SARGENT u. A. ir auf dem Nomenclatur-Standpunkt der Natürlichen BE 
familien und des deutschen Usus stehen, ist der nicht zweifelhafte Name A. dasycarpum be- 
lassen. (Drd.) 
3) BROWN, FORREST B. H.: A botanical Survey of the Huron River Valley II. The plant 
Societies of the Bayou at Nies Botanical Gazette XL, p. 272. Oct. 1905. 
4) MAcMILLAN, CoN On the Formation of circular Muskeags in tamarack Swamps- 
Bulletin Torrey Botanical Be XXXII: 500—507 with plates. 
Harshberger, Survey N.-America, : 26 
